The modification of triglycerides to obtain mixed ester products useful for lubricating and other applications is known. U.S. Pat. No. 3,202,607 discloses the ethoxylation of castor oil and the use of aqueous dispersions of these adducts as metal working fluids. In British Pat. No. 847,517 two mols triglyceride and one mol polyethylene glycol are interesterified to obtain products which are mixtures of mono-, di- and triglcerides and mono- and diesters of polyethylene glycol. The reaction of castor oil with a polyoxyalkylene glycol and an organic dicarboxy acid, such as diglycolic acid or phthalic anhydride, is taught by U.S. Pat. No. 2,925,429. These products are employed for resolving water-in-oil emulsions. U.S. Pat. No. 2,971,923 discloses similar products useful for breaking petroleum emulsions and desalting mineral oils.
The ester lubricants disclosed in U.S. Pat. No. 3,720,695 have utility in a wide variety of use areas and are obtained by transesterifying castor oil with polyoxyethylene glycol of molecular weight greater than 1000 and then, in a separate and distinct step, esterifying the available hydroxyl groups with a mono- or dicarboxylic acid. In copending application Ser. No. 438,283 now U.S. Pat. No. 3,928,401, significantly improved water soluble mixed ester products have been obtained by reaction of a triglyceride with a short-chain mono- or dicarboxylic acid and a low molecular weight polyoxyethylene glycol in a single-step operation.